Centrifugation of target material using a centrifuge vessel holding the target material for processing is widely used in biologic laboratory operations. In some cases, the material of interest remains in fluid in the vessel, allowing it to be decanted from the vessel while leaving behind fluid residue. On other occasions, the target material of interest is centrifuged to a pellet form. The fluid component or supernatant can be removed, leaving the target material of interest in the vessel. If the target material comprises live cells, the pellet method can be used to concentrate the cells to a smaller volume and/or to wash the cells of one suspension media and replace it with a different suspension media.
When processing live cells for clinical or therapeutic use, it can be desirable to process the live cells within one or more closed vessels and reduce, if not minimize, the stress and/or distress experienced by the cell population. Closed vessels allow the processing to proceed in a lower grade clean room than would otherwise be needed for open processing. To minimize stress, the processing can be less aggressive. In particular, the methods of cell concentration and washing may rely on the integrity of a cell pellet at the bottom of the centrifuge vessel to avoid cell losses when the supernatant is removed. While the cells may be stressed by the process of pellet creation, they can also be further stressed or distressed by the action of re-suspending the pellet. The processing can be particularly difficult when the cells in question are present in a limited number. The compromise between pellet integrity and re-suspension vigor are typically conflicting requirements.